This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 24 |
| 5 | 528 |
| 6 | 4648 |
| 7 | 26224 |
| 8 | 112666 |
| 9 | 401424 |
| 10 | 1246000 |
| 11 | 3476368 |
| 12 | 8905432 |
| 13 | 21266208 |
| 14 | 47875272 |
| 15 | 102482048 |
| 16 | 210000931 |
| 17 | 414160240 |
| 18 | 789572072 |
| 19 | 1460372624 |
| 20 | 2628456428 |
| 21 | 4615495808 |
| 22 | 7924479264 |
| 23 | 13328517504 |
| 24 | 21997272036 |
| 25 | 35674700896 |
| 26 | 56926058920 |
| 27 | 89477437120 |